Ac line voltage drop indicator plug

ABSTRACT

An AC line voltage-drop indicator plug comprises a small hollow body, from the rear of which project the plug prongs for insertion into a wall outlet. Within the body is contained an electrical circuit consisting of a silicon rectifier and a neon lamp blinker circuit having a variable resistor with a rotatable terminal. The front face of the body has a transparent portion through which the blinking of the neon lamp may be observed, and a rotatable shaft projecting through this face, which is connected to the variable resistor for varying the voltage. To the outer end of the shaft is connected an indicator knob intended to designate, on a scale on the front face, the minimum voltage at which the lamp begins to blink, which is calibrated to be the true voltage in the line.

United States Patent Woroble [54] AC LINE VOLTAGE DROP INDICATOR PLUG [72] Inventor: Joseph Woroble, 55 Morgan Place,

North Arlington, NJ. 07032 [22] Filed: Nov. 25, 1970 [21] Appl. No.: 92,567

[52] US. Cl ..324/119, 324/122 [451 Sept. 26, 1972 Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Ernest F. Karlsen AttorneyPeter J. Gaylor 5 7] ABSTRACT An AC line voltage-drop indicator plug comprises a small hollow body, from the rear of which project the plug prongs for insertion into a wall outlet. Within the body is contained an electrical circuit consisting of a silicon rectifier and a neon lamp blinker circuit having a variable resistor with a rotatable terminal. The front face of the body has a transparent portion through which the blinking of the neon lamp may be observed, and a rotatable shaft projecting through this face, which is connected to the variable resistor for varying the voltage. To the outer end of the shaft is connected an indicator knob intended to designate, on a scale on the front face, the minimum voltage at which the lamp begins to blink, which is calibrated to be the true voltage in the line.

3 Claims, 6 Drawing Figures 5 ya I4 27 PATENTEDSEP26 1912 3. 694.749 sum 1 or 2 FIG. 2

FIG. 3

INVENTOR. JOSE PH WOROBLE ATTORNEY PATENTEDSEP26 1972 3594.749

sum 2 or 2 I6 v W I9 FIG- 4 l6 l5 1 23 I8 T 1 20 I9 25 FIG. 5

l .\'VE1'\'TOR. JOSEPH WOROBLE ATTORNEY FIG. 6

AC LINE VOLTAGE DROP INDICATOR PLUG BACKGROUND OF THE INVENTION This invention relates to an indicator plug which may be inserted in a suitable wall receptacle, for example, for reading correct voltages of AC electric lines, and particularly, for determining the drop in line voltage at that point.

In recent years, power companies have been forced to reduce line voltages, particularly during the summer, when air conditioning loads were at their peaks. When line voltage drops, for example from 120 volts to about 112 volts, more or less, television reception becomes considerably impaired. For example, black-and-white sets suffer a shrinkage in picture size. In the case of color sets, however, the effect is much worse, and not only does the picture get out of focus, but color is also affected. Viewers of television sets, who are unaware of the voltage loss effect, often attempt to correct the picture by turning knobs and making other adjustments with the result that, when the repairman is called, the readjustment becomes much more serious than otherwise. Also, very often, the lead line from the electrical outlet receptacle to the set may be faulty by having a break, for example, whichv often entails additional detailed inspection. Furthermore, there may be a loose connection in the wiring inside of the wall receptacle which cannot be readily detected. Some of the aforesaid difficulties might be detected with an AC voltmeter, but such units are too expensive for the average householder, and too clumsy and too heavy to use for the TV repairman.

In applicants US. Pat. Nos. 3,271,673 and 3,452,277, various high voltage test probes have been described, wherein a blinker electrical circuit is employed. However, these devices do not employ voltage rectifiers, and they cannot be used as wall plugs, as is done in the case of the present invention.

SUMMARY OF THE INVENTION According to the present invention, practically all of the aforesaid difficulties may be overcome by the use of a small inexpensive, but yet quite accurate, voltagedrop indicator plug which may be plugged into any socket or electrical outlet. The unit comprises a hollow housing containing an electrical neon lamp blinker circuit and a rectifier, such as a silicon rectifier for converting the AC entering the unit, to DC. The front face of the housing has a window for observing the blinking of the neon lamp, as well as a calibrated dial and rotatable indicator knob for indicating the line voltage.

By turning the knob until blinking occurs, the true line voltage may be readily read on the scale. Such a unit may be used not only by the public, but also by TV repairmen, or even by an electrician who is interested in locating line trouble spots. If a loose connection is suspected in a line having the conventional dual outlet receptacle, for example, the line voltage-drop indicator plug of the present invention may be plugged into the upper outlet, while an appliance of high load capacity, such as a 1,000 watt flatiron may be plugged into the lower socket. Thereafter, the knob of the plug unit is turned until the neon lamp therein begins blinking. Then, the lamp is watched, and if the lamp goes out momentarily and then again begins to blink, it is a sign that the line is faulty and probably has a loose or corroded connection.

Another use for the plug'of the present invention is its ability to indicate overloading of lines. By plugging into a loaded line receptacle. the unit of the present invention, and noting the actual indicated voltage, in comparison with the nonloaded line voltage, overloading can be readily detected. For example, if the voltage of a normally-unloaded volt line reads, say ll5 volts at the receptacle, it is a good indication that the particular line is dangerously overloaded, and might result in a fire. This is of particular importance during the summer air conditioning power drain, or during the Christmas season, for example, when strings of colored lamps are employed for decoration.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more readily understood by reference to the accompanying drawings, in which:

FIG. 1 depicts a front elevational view of an AC line voltage drop indicator plug of the present invention designated to measure in the I20 or 220 volt ranges;

FIG. 2 illustrates a side elevational view of the same P g;

FIG. 3 shows a rear elevational view thereof; FIG. 4 presents a diagram of the circuit-for a 120 volt line, incorporated in the body of the plug shown in FIGS. 1 to 3;

FIG. 5 illustrates a diagram of a modified circuit for a plug in the 120 volt range, and

FIG. 6 shows a diagram of a circuit for a 220 volt AC line, to be incorporated into a plug of the present invention.

The same numerals refer to the same or similar parts in the various figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring again to the drawings, numeral 10 indicates generally a hollow circular body preferably made of insulating plastic, and having a circular side 11, front face plate 12, and back plate 13. This hollow body incorporates the elements of the respective circuits, each of which is described in detail in FIGS. 4 to Each of the circuits depicted comprise a voltage rectifier 15, such as a silicon rectifier, and a neon lamp blinker circuit, employing lamp 14. In FIG. 4, the circuit for the 120 volt AC line voltage measurement includes two plug prong members 16 and 17, which project from rear plate 13 of plug body 10. Connected to the rear of plug prong 16, at 23, is one end of fixed resistor 18. To the other end of resistor 18 is connected the fixed end of variable resistance 19. Movable end 20 of resistor 19 is connected to the end of fixed resistance 21. End 20 is moved by rotatable knob 22 (FIGS. l-2). The other end of resistance 21 is connected at 26 to a terminal of silicon rectifier 15. One end of another fixed resistance 22 is connected to the other terminal of rectifier 15, while the other end of resistor 22 is connected to the rear of prong 17.

One terminal 24 of neon lamp 14 is connected to the rear of prong 16 at 23, while the other terminal 25 is connected to the inner terminal of rectifier 15. A capacitor is connected across terminals 24 and 25 of lamp 14.

In the measurement of the voltage of 120 volt lines, resistor 18 may have a resistance of, say 1% megohm,

while resistor 19 can also have a resistance of 1% megohm, resistor 21, say 910,000 ohms, and resistance 22, 680,000 ohms. With such an arrangement, front face plate 12 is provided with a dial 28, calibrated say, between l05 and 120 volts. The top of face plate 12 may be coated with an opaque coating, except for a transparent window 29, through which may be viewed the blinking of neon lamp 14. When prongs 16 and 17 are plugged into a suitable receptacle, knob 22 is turned from the high to the low values of scale 28 until neon lamp 14 can be observed to blink through window 29. The reading of pointer 22' on scale 28 will give the line voltage within 1 volt, or even less.

In the circuit shown in FIG. 5, the modification involves connecting silicon rectifier 15 to prong 16 ahead of, or outside of, junction 23. Otherwise, the circuit is the same as that depicted in FIG. 4.

The circuit depicted in FIG. 6 for measuring 220 volt line voltages is similar to those shown in FIGS. 4 and 5 with the exception that an additional resistance 31 of, say 1% megohm value, is inserted between prong 16 and rectifier 15. Also, the value of resistance 22 is raised to, say 1 megohm, and the prongs 16 and 17 are also desirably accompanied by a third conventional grounding plug prong. Of course, scale 28, which may extend over a span of, say 145", would also have to be calibrated for the higher reading range. It will be noted that shaft 30, to which knob 22 is attached, projects through front face .12 and is the shaft which rotates the movable terminal of variable resistance 19.

The present invention offers an inexpensive, small, convenient and fairly accurate means for indicating line voltage drop. Since the lamp consumes very little current, the plug may be left inserted in a wall receptacle in blinking voltage-indicating condition, so that line voltage drop can be readily detected when the lamp ceases to blink. Scale 28 may extend over a span of about 145 to about 230.

I claim:

1. An AC line voltage-drop indicator plug, comprismg:

a small hollow body made of insulating material and having a rear plate and a front plate, said front plate having a window,

a pair of spaced plug prongs extending from within said rear plate, through said latter plate and projecting outwardly sufficientlyto enable plugging thereof into an electrical line outlet receptacle,

an electrical circuit disposed within said body and connected across said prongs, and incorporating:

a voltage rectifier connected at one terminal to the rear of one prong,

a first fixed resistance connected at one end to the other terminal of said rectifier,

a variable resistance having a rotatable terminal and a fixed terminal, the latter being connected to the other end of said first resistance,

a second fixed resistance having one end connected to the rotatable terminal ofthe variable resistance,

a third resistance having its one end connected to the rear of the other prong, and its other end connected to the other end of the second fixed resistance, a neon lamp disposed m viewable relation with an indicator knob attached to the other end of said shaft, and

a scale disposed on the outer surface of said first plate around said shaft and designed to indicate the minimum voltage at an indicator position when said lamp begins to blink.

2. An AC line voltage drop indicator plug, according to claim 1, wherein the electrical circuit comprises:

a first fixed resistance having one end connected to the rear of a first prong,

a variable resistance having a fixed end connected to the other end of said first resistance, and having a movable terminal,

a second fixed resistance having one end connected to the movable terminal of said variable resistance,

a rectifier having its first terminal connected to the other end of said second resistance,

a third fixed resistance having one end connected to the rear of the other prong and its other end connected to the other terminal of said rectifier,

a neon lamp having one terminal connected to the rear of said first prong, and its other terminal connected to said first terminal of said rectifier, and

a capacitor connected across the terminals of said lamp.

3. An AC line voltage drop indicator plug, according to claim 1, in which a fixed resistance, is inserted between the rear of the first-named prong and therectifier. 

1. An AC line voltage-drop indicator plug, comprising: a small hollow body made of insulating material and having a rear plate and a front plate, said front plate having a window, a pair of spaced plug prongs extending from within said rear plate, through said latter plate and projecting outwardly sufficiently to enable plugging thereof into an electrical line outlet receptacle, an electrical circuit disposed within said body and connected across said prongs, and incorporating: a voltage rectifier connected at one terminal to the rear of one prong, a first fixed resistance connected at one end to the other terminal of said rectifier, a variable resistance having a rotatable terminal and a fixed terminal, the latter being connected to the other end of said first resistance, a second fixed resistance having one end connected to the rotatable terminal of the variable resistance, a third resistance having its one end connected to the rear of the other prong, and its other end connected to the other end of the second fixed resistance, a neon lamp disposed in viewable relation with said window and having one terminal connected to the other terminal of said rectifier, and its other terminal connected between the second and third fixed resistances, and a capacitor connected across the terminals of said lamp, a rotatable shaft connected at one end to the rotatable terminal of said variable resistor for varying the DC voltage passing through said circuit, and having an end projecting outwardly through said front plate, an indicator knob attached to the other end of said shaft, and a scale disposed on the outer surface of said first plate around said shaft and designed to indicate the minimum voltage at an indicator position when said lamp begins to blink.
 2. An AC line voltage drop indicator plug, according to claim 1, wherein the electrical circuit comprises: a first fixed resistance having one end connected to the rear of a first prong, a variable resistance having a fixed end connected to the other end of said first resistance, and having a movable terminal, a second fixed resistance having one end connected to the movable terminal of said variable resistance, a rectifier having its first terminal connected to the other end of said second resistance, a third fixed resistance having one end connected to the rear of the other prong and its other end connected to the other terminal of said rectifier, a neon lamp having one terminal connected to the rear of said first prong, and its other terminal connected to said first terminal of said rectifier, and a capacitor connected across the terminals of said lamp.
 3. An AC line voltage drop indicator plug, according to claim 1, in which a fixed resistance is inserted between the rear of the first-named prong and the rectifier. 